The present invention relates to lifting apparatus, and more particularly, in conjunction with hoist means, devices for grasping, raising, moving, and releasing articles.
Various industries require lifting of relatively heavy articles such as steel cylinders, barrels, drums, paper rolls, boxes, crates, and articles of other shapes. By way of example, in the steel manufacturing industry, cylindrical spacers are used to build rolls for straightening steel. The spacers are made of steel and are stacked coaxially for storage on the mill floor, and may be on the order of, for example, 24 inches (61 cm) outer diameter and from 2 inches (5 cm) to 8 inches (20 cm) tall. In general, such spacers have been moved from place to place within a steel mill by use of a conventional grapple suspended from hoist means, such as a crane or a forklift. Other objects including coils, bars, and similar articles may be moved similarly.
In moving stacked cylindrical spacers, a forklift operator must get off the forklift, a crane operator must leave the crane, or another worker must be used, in order to mount the grapple on the top spacer on the stack. The grapple's individual hooks must be lodged between the spacers. Common means of providing room between spacers is to use hammers, chisels, and screwdrivers to pry the top spacer upward. Safety is compromised because of the chance of injuries such as back strain or crushed fingers while mounting the grapple on the spacer. Further, assembly of the straightener rolls is excessively time consuming, using both the capability of the workers and the equipment that could be used to perform other tasks.
Additional types of conventional grapples exist in addition to those that rely on hooks to support an object from the bottom. Where an object to be lifted provides a protrusion such as a flange at its upper edge, some conventional grapples have operated on the principle of grasping the protrusion or the object immediately under the protrusion. Others clamp onto the object directly, but may be inadequate in the amount of force applied, complex to fabricate, difficult to use, or any combination thereof. Further, some conventional grapples include means for automatically or semi-automatically latching the grapple hooks or grips in position, including either being retracted or engaged onto an article to be lifted. This latching means is often complicated, either in manufacture, use, or both, and may also be unreliable.
Accordingly, there exists a need for a lifter that is relatively safe for use by workers and can be quicker to use than a conventional grapple. The lifter should be reliable and simple to use.